Xorshift128+ isn't -- and wasn't meant to be -- a CSPRNG. It's not like anyone is gonna be using this in place of Yarrow or Fortuna, for example (or so we hope!), or using it to generate important private keys (i.e., for GPG or TLS) or anything like that.
This is about whether the output of the PRNG passes statistical tests for randomness. In a previous blog post by John D. Cook we saw that it failed the PractRand statistical test suite [1], and now we see that it also fails the older TestU01 suite, too.
When Xorshift128+ and Xoroshiro128+ were launched, they were claimed to be statistically excellent. Those claims have been shown to be false.
[1] https://www.johndcook.com/blog/2017/08/14/testing-rngs-with-...